Which modality shows 2 lp/mm resolution?

• A. Fluoroscopy
• B. Digital radiography
• C. Computed radiography
• D. Ultrasonography

Answer: (D)

Line pairs per millimeter measure how finely an imaging modality can separate adjacent details; higher lp/mm means finer spatial resolution. Ultrasound resolution depends on the transducer frequency: higher frequency gives crisper detail but less depth. In typical clinical practice, standard ultrasound probes provide about 2 lp/mm of spatial resolution, which sits at a moderate level of detail suitable for real-time imaging of soft tissues. The radiographic modalities listed are designed for static imaging with greater detail than 2 lp/mm, so they usually offer higher spatial resolution than ultrasound. Therefore, ultrasound is the modality most commonly associated with around 2 lp/mm resolution.